Natural gas is used as a fuel generating over 27% of the total U.S. power supplied by electricity. It is also used in factories, homes, chemical processing plants and refineries as a fuel or feed stock. Once produced, natural gas is dehydrated, processed, compressed and transported from natural gas wells to points of use through extensive pipeline networks.
Natural gas naturally contains solid and liquid contaminants from production reservoirs. As it also picks up contamination from dehydration, processing, and compression operations, natural gas requires multiple stages of contaminant removal through filtration and separation processes. The filtration separation stages are located prior to and following dehydration, processing, and compression plants located along the pipeline networks.
A filter separator is a pressure vessel that directs a gas stream to travel through multiple filter elements, configured in a parallel arrangement, such that the gas stream is divided to equally flow through the filter elements. The filter elements are constructed of a porous filter media and may be supported by a plastic or metal flow support core and sealed on each end by caps with a gasket attached to seal the cartridges to sealing surfaces within the pressure vessel. Positive, robust cartridge sealing is required to force the entire gas stream through the filter media, not allowing contamination to bypass the filter media and travel downstream.
As the gas stream travels through the filter media, solid particles will be stopped and captured on and within the filter media. Small liquid droplets and aerosols will travel with the gas stream relatively equally to each of the filter elements. As the gas stream enters the porous filter media, the liquid aerosols and mist will be trapped within the filter media. The liquid aerosols and mist trapped within the filter media will converge together and join forming larger liquid droplets. The converging of liquid droplets within a filter media to form larger droplets is a process referred to as coalescing.
The filtered gas stream will exit the filter media with the larger coalesced liquid droplets. Once the gas stream exits the filter media, it will normally travel to a mist extraction device configured within the same pressure vessel. The mist extraction device can be an impaction-type high surface area structure such as a wire mesh pad or a vane-type separator, or a bank of cyclonic devices designed to extract liquid droplets from the filtered gas stream. Filter elements trap and remove solid particles and receive smaller liquid droplets and aerosols, coalesce them, and release them as larger liquid droplets. The coalescing mechanism creates liquid droplets that are large enough to be effectively removed by the unit's second stage mist extractor.
The filter separator filters solids and separates liquids from a gas stream. Filter separators have been considered as standard equipment in the natural gas industry since the 1950's and can be found on most, if not all, natural gas pipelines.
A typical filter element sealing assembly includes a cartridge-sealing seat welded to a flow pipe, a support bar, a threaded bolt, seal plate, nut, washer, and gasket. The flow pipe will be welded to a support plate that will be welded to the pressure vessels inside surface. The support plate will separate the pressure vessel's first stage from its second stage and will act as a stopping point designed to force the unfiltered gas through the filter elements sealed on the filter element sealing assembly. The filter element slides over a “z” shaped support bar.
Once fully engaged, the filter element seal gasket will contact the sealing assembly. Next, a seal plate will be installed and pressed up against the filter element's opposite end, followed by a gasket, washer, and sealing nut. The sealing nut will be tightened to compress the sealing plate against the filter element and the filter element against the sealing seat. The process to replace a typical filter element in the prior art is typically slow, but provides a positive seal of the filter element preventing contaminant bypass.
Furthermore, the process is dependent on the operator following instructions, including properly installing the filter element and the associated hardware. For example, the operator needs to apply the appropriate amount of torque to the sealing nut to form a positive seal between the filter element and the sealing seat. If the operator over-torques the sealing nut and the filter element compresses the support core to the point that it bends and loses contact with its sealing surface contaminant bypass will occur. Once the contact is lost between the support core and the sealing surface it will allow contaminants to bypass the filter media. As torque wrenches are not normally available to the operator, it leaves trying to determine the narrow sealing torque gap up to the operator's feel and judgment. This makes the improper installation of the filter element assembly a possible occurrence that could result in contaminants being able to bypass the filter media.
Thus, there remains a need for a filter element with sealing technology that eliminates the need for an operator to estimate the amount of torque required to properly seal a filter element on the sealing seat, while also limiting the need to use hardware to effectively and efficiently replace filter elements in pressure vessel assemblies. The invention provides such a filter element sealing assembly. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.